<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            margin-top: 10px;
        }
        .box1{
            width: 500px;
            height: 100px;
            border: 1px solid #000;
            padding: 10px 20px;
            border-top-left-radius: 20px;
            border-bottom-right-radius: 20px;
            
        }
        .box2{
            width: 300px;
            height: 50px;
            border-top: 1px solid red;
            border-bottom: 1px solid red;
        }
        .box3{
            width: 100px;
            height: 100px;
            border: 3px solid green;
            border-radius: 50%;
        }
        .box4{
            width: 100px;
            height: 50px;
            border: 5px dotted red;
        }
        .box5{
            width: 100px;
            height: 50px;
            border: 5px dashed red;
        }
    </style>
</head>
<body>
    <div class="box1">有四条边框</div>
    <div class="box2">有两条边框</div>
    <div class="box3">圆角边框</div>
    <div class="box4">点线</div>
    <div class="box5">虚线</div>
</body>
</html>